When dealing with the clinical symptoms of Parkinson's disease, the three largest characteristics that are often observed are tremors, bradykinesia, and rigidity. It is considered that a decrease in dopamine in the brain causes Parkinson's disease. Therefore, the treatment of Parkinson's disease is carried out by administering dopamine with a form of precursor, which regulates dopamine metabolism or uses dopamine agonist. There have been several known remedies for Parkinson's disease, and typical examples include levodopa, sinemet, atropine sulfate, scopolamine, dopamine agonist, bromocriptine mesylate, and selegiline. However, these drugs suffer from a few drawbacks, such as tolerance to the drug after prolonged administration, side effects, failure to prevent the progress of the disease and so on.
Tablets made from a composition of levodopa and carbidopa are also commonly used to treat Parkinson's disease. Carbidopa is an aromatic L-amino acid decarboxylase inhibitor, which can efficiently reduce the transformation of levodopa to dopamine and raise the concentration of levodopa and dopamine that functions in the brain. In addition, U.S. Pat. No. 5,446,194 also discloses a medicine, called entacapone, for Parkinson's disease treatment. The medicine is a catechol-O-methyl transferase (COMT) inhibitor, which is used with levodopa to raise the concentration of levodopa in the brain and increase the bioavailability of levodopa. Patients can take a tablet comprising levodopa and carbidopa as well as a tablet containing entacapone several times a day to control their symptoms. However, it is a burden for patients suffering from dysphagia or tremors to take two tablets each time they need to administer treatment.
Therefore, the current treatment for Parkinson's disease lacks an effective method that combines the convenience of taking the medicine and having better curative effects for Parkinson's disease.